BIM is the representation of the digital evolution from traditional 2D model to 3D mode and even to 4D model (scheduling) and 5D model (cost estimating) with a database through the building lifecycle. Special capabilities of parametric modeling and interoperability facilitate this evolution process as detailed below:
2.9.1 3D BIM Application
BIM model is an intelligent visual and data based process that gives architecture, engineering, and construction (AEC) experts the perception and authoring tools in delivering a more efficient plan, design, construct as well as a facility management (Davies and Barnes, 2015). Build it twice once virtually and once physically is the process benefit encouraging virtual construction. Building Information Modelling presents various 3D Models such as design models (architectural, structural, MEP – Mechanical, Electrical and Plumbing and site/civil structural models), Construction model involving federating and splitting of design models into construction sequences. 3D BIM model contains advanced information such as drawings,
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materials, components, schedules, energy analysis, HVAC systems, COBie data sheets, and more. This allows information to be secured as well as available to each key discipline team member to access and contribute their intelligence to the project. The model simplifies the collaboration workflow of a project as well as savings in costs, time, and human errors. Any change, alteration or variations to the model instantly updates all the data reflecting in update of sources such as schedules, constructability, costs and risks (Andersson et al, 2016). 3D BIM models export IFC files formats strengthening an effective and flexible collaborative platform to various software within a multi-disciplinary team. This can then be taken to the next level with constructability and coordination, 4D scheduling, and 5D cost planning.
Model walkthroughs and clash detections are made possible within a 3D BIM environment providing great visualisation tool, exposing risks, identifying potential site issues and resolving perceived construction problems enabling contractors and designers to work more effectively together. By identifying potential constructability issues early in the design phase, clashes that would have been detected so late causing construction delays and needing quick decisions would be identified and resolved during design coordination of the 3D model of varying building systems including subcontractors integrated shop drawings before actual construction starts. Schedule simulation possesses capabilities that allows project owner an insight into evolving construction process and acts as a useful marketing tool for the project team while enabling the contractors to visualise how the entire building or facility will develop (Davies and Barnes, 2015). In 3D BIM virtual mock-ups model is made available for better understanding and aesthetical and functional project decisions, helping the owner to test a fraction of the physical construction of the building. Confidence for the use of prefabricated offsite products increases with the visualisation and simulation of the model having greater assurance due to integrated level of construction information that manufactured products will fit once transported to construction site for installation (fit for intended designed purpose).
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Deployment of 3D model for differing functions within level 2 BIM process has generated other dimensional references such as 4D (adding timeline to the model), 5D (the linking of 3D BIM model data to the 5th dimension to generate cost data and cost schedules), 6D (facility management) and 7D (the green model – sustainability). Potentially 3D BIM model has become a platform that improves all project processes cross-functioning through planning, design, construction, operation and maintenance stages.
2.9.2 4D BIM Application
Traditionally, “planning consists of those processes performed to establish the total scope of the efforts, define and refine the objectives, and develop the course of action required to attain those objectives. The planning processes develop the Project Management plan and the Project documents that will be used to carry out the project” (PMBOK, 2013). Project planning is therefore closely aligned with developing the project strategy. The difference is that planning is focused on optimising the sequencing of the work as a prerequisite to scheduling, which on its own is a key subset of planning (developing the overall project strategy) (Sarker et al, 2012). As Information is frequently limited, planning then requires good understanding and experience of the project work starting early in the design phase, and involving all key stakeholders (PMBOK, 2009). The main benefits of planning and construction scheduling are gained by engaging in the process – therefore the planning process should be participatory and evolutionary. Project planning is viewed as a common starting point from which to adapt as project detail evolves and not as a script. Plans are flexible and adaptable, allowing the opportunity to pursue a variety of options as the more detailed working schedule is developed. Planning is the early process of determining how the work will be accomplished and involves analysing alternatives and developing method statements. This is the platform where 4D BIM application is leveraged to strengthen the choice of alternatives and extracting accurate scheduling information from a BIM model.
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4D BIM modelling is adding the fourth-dimension schedule to the 3D model. The fourth- dimension model links the 3D elements with the project delivery timeline to provide users a virtual simulation of the project in the 4D environment. The linkage to project timeline makes it possible to graphically visualize the projects schedule and users can simulate the building site and construction at any point developing real time schedule and workspace planning. This type of simulation provides considerable insight and allows for early detection of planning errors. Instead of realizing planning mistakes later on in the construction phase, and having to resolve problems on site which can be very costly, mistakes can be eliminated already in the design phase (Eastman et al., 2008). Meaning that 4D BIM application has an integrated capability to verify and optimize site logistics and operations (like temporary components such as crane, traffic access, lorries, lifts and large items) to visually plan and manage space utilization of a construction site throughout the project ((Davies and Barnes, 2015). Various alternative solutions of conducting construction can be simulated and weighted against each other to find the most beneficial solution (Eastman, et al., 2008). By adding ‘time’ to the information in the project model (linking attributes to the construction programme), it becomes possible for contractors to review the construction of the building. 4D tool can be particularly useful for a challenging construction site or a large complex project to examine the critical path activities, consider real time work schedules, handle logistics such as craneage and deliveries and to redefine in general terms how the building is to be constructed (RIBA, 2012). An advanced interoperability process will make it easier to consider more buildability options, allowing a number of construction options to be prepared and translated into a 3D representation of the construction process. With progressive model update reflecting activity on site, 4D application can be a useful tool in reviewing progress against the baselined programme and highlighting where progress is behind. The objective of maximizing the efficiency of the project strategy with respect to cost and time is to be balanced against the risks associated with new methods of working and the overall quality of the finished
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deliverables. Changes in design within the BIM model can be identified and impact on critical activities known with overall indication and assessment of the corresponding impact on the overall project delivery. The tool can also be useful in exploring ways to make up time lost. Conversely, the contract administrator can deploy the programme for assessing delays and any applications for an extension of time (RIBA, 2012).
2.9.3 5D BIM Application
Construction suppliers traditionally determine project cost, requirements and material quantities by performing manual takeoffs, interpreting data manually while completing costing tasks, a process integrated with potentials for human error (RICS, 2015). Traditionally, a CAD drawing is scanned and manually interpreted to calculate quantities that make up building cost (Pittard and Sell, 2016) in contrast to digital measurement software like CostX 6.6 that allows users to strip a building model of its layers, analyze and examine individual designs in isolation for visual takeoff. This eliminates error prone process for manual takeoff and manual spreadsheet reporting formats improving management of cost information, structured information exchange, management of cost data, efficient cost modelling and accurate data interpretation. With 5D BIM process, digital construction information allows contractors, employers and the project team to generate accurate cost and essential estimating information with model element attributes like size, area, object family type, and productivity projections (Davies and Barnes, 2015). 5D BIM model is the linking of the fifth dimension to the 3D BIM model extracting non-graphical data and model attributes to generate cost information and material quantities within a level 2 BIM collaborative environment. Evolving design changes within the model automatically adjusts to improve progressive accuracy of cost performance. 5D model is expected to link BIM model to cost data through a digital model information for quantity takeoff generating accurate project cost estimation. The ability of BIM models to generate cost information and quantity schedules will allow for faster cost value of a given design (RIBA, 2012). However, given that the
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model mapping of item properties is not yet embedded in BIM objects, Crowley (2013); Monteiro and Martins (2013) observes that the current QS practice appends object properties in the estimating tool for takeoff suitability. If the model objects are not properly coded in the design software to suit the QS functions then the first step towards supporting cost and quantity schedule, would be to develop a Cost Breakdown Structure (CBS) associated to a Work Breakdown Structure (WBS) and units that enables the QS populate cost plan easily (Drogemuller and Tucker, 2003).
Option appraisal of different design alternatives at the early stage is more accurately assessed and with the designers in possession of the cost information at their fingertips, the iterative design process will be accelerated, making it more likely that the designs are aligned with client’s budget. How cost consultants will provide and integrate cost information into the model along with the methods of outputting area and quantity information in a way that will translate into a reliable cost plan that takes due cognizance of project specific cost drivers and market trend will need serious consideration.
2.9.4 6D BIM Application
6D BIM refers to the linking of the 3D model information to a sixth dimension for lifecycle management of a facility (operations and maintenance) and uses a standard Public Available Specification (PAS) 1192:3 to guide user’s implementation. PAS 1192:3 is a companion document to PAS1192:2 (capital/delivery phase of a project) focusing on the operational phase of asset regardless of the commissioning route and commencing at handover (BSI, 2014). 6D also refers to as-built BIM model linked with asset management information of building’s components. This allows optimisation of whole life cost of managing portfolio of assets though can be complex and vary based on the utilisation requirements. Generated construction model is updated (as built and not as intended) with accurate ‘as built’ information and handed to the owner at completion of the construction final stage in COBie format. This is part of the ambitious UK Government construction strategy for fully
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collaborative 3D BIM with all project and asset information, documentation and data being electronic from 2016 (Cabinet Office, 2011) – thus representing minimum requirement for Level 2 BIM on publicly procured projects.
COBie is a structured asset information for the commissioning, operation and maintenance of an asset often in a neutral spreadsheet format that will be used to supply data to the organisation to populate decision making tools and asset management system (BSI, 2014). Information within COBie is data arranged and processed into meaningful patterns, and put into context for operational use. Operation and maintenance (O&M) manual is created including warranty information for model elements in consort with data sensor tools with ability to capture and feedback future maintenance data when and where required. Some 6D application software tools have capabilities that deals specifically on virtual navigation. This is done through a model linking any type of document to model element and same time accessing product information and maintenance manual database through an integrated programme that signals if installed objects are within their warranty periods with capabilities for distance inspection of installed products. This level of information provision for the O&M purposes enhances efficient cost control and ultimate cost savings in managing, and evaluating portfolio of assets (BSI, 2014).